Piston rod bearing assembly of reciprocating piston engine

Abstract

A bearing assembly for a piston rod of a linearly reciprocating piston type engine having a cylinder (11), a piston (12) movable axially in cylinder (11), at least one piston rod (13) secured to and projecting axially from one side of the piston to be received in a respective bearing assembly (17) mounted in a cover assembly at one end of the cylinder and which guides the movement of the piston/piston rod assembly, said bearing assembly comprising: an inner annular array of balls (18) which roll on the cylindrical outer surface of the piston rod (13) during its reciprocation, and housed in an annular space defined between the cylindrical outer surface of rod (13) and a sleeve (19); bearings (20) which rotatably mount sleeve (19); and means for rotating the sleeve (19) about the axis of the piston rod (13) so as to apply continuous rotation to the balls during each cycle of reciprocation of the piston rod and thereby enable a hydrodynamic lubrication of the bearing assembly.

I claim: 
     
       1. A linear bearing assembly comprising: an annular array of balls receiving a linearly reciprocatable rod;   a sleeve radially spaced from the axis of the rod to define an annular space in which the array of balls is housed; and   means for applying rotation to the sleeve about said axis in order to rotate the balls.   
     
     
       2. A bearing assembly according to claim 1, and arranged so that the balls can roll on the cylindrical surface of the rod to carry out linear movement and also circumferential movement relative thereto. 
     
     
       3. A linear bearing assembly comprising: an annular array of balls receiving a linearly movable rod;   a housing in which the balls are received; and   means for applying rotation to the balls continuously about respective axes extending generally parallel to the axis of the rod, and at such a speed that hydrodynamic lubrication of the bearing surfaces can be maintained when lubricant is present in the bearing assembly.   
     
     
       4. A linearly reciprocating piston engine comprising: a cylinder;   a piston movable axially in said cylinder;   a piston rod secured to and projecting from one side of the piston, said piston rod extending parallel to the axis of the piston and being movable with the piston in a fixed plane parallel to the axis of the cylinder;   a cover assembly at one end of the cylinder and facing said one side of the piston;   an opening formed in said cover assembly through which the piston rod extends; and,   a bearing assembly mounted on said cover assembly and arranged to guide the linear reciprocating movement of the piston rod, said bearing assembly comprising an annular array of balls surrounding and making contact with the cylindrical periphery of the piston rod, and a housing in which the balls are received; and,   means for applying rotation to the balls about respective axes extending generally parallel to the axis of the piston rod, during at least part of the cycle of reciprocating movement of the rod.   
     
     
       5. An engine according to claim 4, and arranged so that the balls can roll on the cylindrical surface of the rod to move linearly and also circumferentially relative to the rod. 
     
     
       6. An engine according to claim 5, including means for rotating said piston rod, in order to rotate the balls about said axes extending parallel to the axis of the piston rod. 
     
     
       7. An engine according to claim 6, in which the piston is linearly reciprocatable in said cylinder substantially without guidance by sliding contact with the inner wall of the cylinder, and a pair of oppositely projecting piston rods is secured one each to a respective one of the opposed working faces of the piston, and extends through a mounting opening in a corresponding cover end plate of the housing and is mounted therein via a respective bearing assembly. 
     
     
       8. An engine according to claim 6, in which said annular array of balls surrounding and making contact with the cylindrical periphery of the piston rod is retained against axial and/or peripheral relative displacement via a cage. 
     
     
       9. An engine according to claim 6, in which the annular array of balls is uncaged, and has its relative axial movement limited between a pair of axially displaced end stops. 
     
     
       10. An engine according to claim 5, in which the cover assembly comprises a cover closing one end of the cylinder and defining an aperture through which the piston rod extends, and a mounting portion connected to the cover and projecting therefrom, and on which said bearing assembly is mounted. 
     
     
       11. An engine according to claim 4, in which said means for applying rotation to the balls about respective axes extending generally parallel to the axis of the piston rod is operative to apply discontinuous rotation, but sufficient that substantially the entire cylindrical surface of the rod is engaged by the balls after a large number of reciprocations of the rod. 
     
     
       12. A linearly reciprocating piston engine comprising: a cylinder;   a piston movable axially in said cylinder;   a piston rod secured to and projecting from one side of the piston, said piston rod extending parallel to the axis of the piston and being movable with the piston in a fixed plane parallel to the axis of the cylinder;   a cover assembly at one end of the cylinder and facing said one side of the piston;   an opening formed in said cover assembly through which the piston rod extends; and,   a bearing assembly mounted in said cover assembly and arranged to guide the linear reciprocating movement of the piston rod:   in which the bearing assembly comprises an annular array of balls surrounding and making contact with the cylindrical periphery of the piston rod; a sleeve radially spaced from the axis of the piston rod to define an annular space in which the array of balls is housed; means rotatably mounting the sleeve in the cover assembly; and means for applying rotation to the sleeve about the axis of the piston rod during linear reciprocation of the latter in order to rotate the balls.   
     
     
       13. An engine according to claim 12, in which said means by which the sleeve is rotatably mounted in the cover opening comprises a further annular array of anti-friction bearings. 
     
     
       14. An engine according to claim 12, including indexing means for applying discontinuous rotation to said sleeve, but such that substantially the entire cylindrical surface of the rod is engaged by the balls after a large number of reciprocations of the rod. 
     
     
       15. A reciprocating piston type of compressor which comprises: a cylinder, a piston mounted for linear reciprocation in said cylinder substantially without guidance by sliding contact with the inner wall of the cylinder, a piston rod rigidly secured to each side of the piston, and a respective ball bearing assembly provided in one end of said cylinder and which receives each piston rod so as to guide the reciprocating movement of the piston, and means for applying continuous rotation to the balls during each cycle of reciprocation of the piston rod so as to maintain a hydrodynamic lubricating effect.